The process of testing groundwater for contamination may be time consuming, expensive, and environmentally unfriendly. Because the results are used to determine future monitoring and/or remediation efforts for which cost can run into millions of dollars, the sampling requires precision. Often it is desirable to retrieve an adequate quantity of chemically and stratigraphically representative samples for analysis. The analysis may include determination of the thickness of a layer of contamination floating on the groundwater surface.
The multipurpose groundwater sampler allows samples to be acquired faster and more efficiently, with less sample loss or interference from sediments and solids and it is quickly field adaptable to retrieve accurate, representative samples of floating contaminant thickness. In accordance with the technique of groundwater sampling, devices of the prior art called bailers are used to retrieve groundwater samples from wells penetrating the water table beneath the ground surface. A bailer consists of a hollow tube with an inlet nozzle and a check valve means at the lower end, and a handle at the top. The bailer is lowered by tether into the well so as to intersect the water table, and fill with water through the bottom nozzle and valve means. The bailer is retrieved to provide a representative water sample for visual and laboratory analysis.
Groundwater sampling bailers of the prior art are commonly produced and sold by a number of manufacturers. These bailers all have certain design features in common which render them inefficient for their intended purpose of sampling groundwater and unreliable for certain other purposes for which there is a concurrent need, such as obtaining a representative thickness of a contaminant, gasoline being an example, floating on the groundwater surfaces. Technicians who use the bailers complain that they fill too slowly and that sediments normally found in the water being sampled cause the devices to leak excessively. Because monitoring sites are remote from a technician's facility, they often complain about the number and amount of equipment they have to carry to complete their sampling.
Voss Technologies produces and sells a makeshift, add-on device for their standard water sampling bailers for those attempting to obtain a sample of floating petroleum contaminants. The device sold by Voss however, has several apparent drawbacks. That device is a separate part which must be purchased, inventoried, brought to the job site, and adapted to a standard bailer. The adapter does not have a means for keeping sediments away from the valve, the adapter has been known to fall off in the well during use, resulting in great expense of time and money attempting retrieval. Further, the device is physically constrained with a fixed distance between the restrictive valve and the fluid inlet with no provision for extending the length in the field to accommodate thicker contaminant layers.
All the groundwater sampling bailers heretofore known suffer from a number of disadvantages and drawbacks:
a) They are made specifically for the one purpose of retrieving a sample of water from below the static water surface. In addition to retrieving a water sample, field technicians often are required to retrieve and measure a representative thickness of floating contaminants such as gasoline. Because it is inconvenient and expensive to carry a multitude of different sampling equipment to each site, technicians attempt to use water-sampling bailers to retrieve a sample of representative thickness of liquids that float on the groundwater surface. Bailers of the prior art are not effective for this purpose because the fluid inlet nozzle is much smaller in diameter than the sample chamber into which the sample is collected. Known bailers of the prior art have nozzle inlet openings of about one half inch in diameter or less to fill a one and one half inch diameter sample chamber. When a bailer with a one half inch diameter nozzle is used to sample a liquid with one inch of stratified contaminant thickness in situ, the bailer will allow less than less than one quarter inch thickness of this layer to accumulate in a one and one half inch diameter sample chamber. The small opening also creates an aerodynamic shape which causes liquids to flow preferentially around the nozzle instead of into the nozzle as the device is lowered into the liquid to be sampled. The thickness of the sample in the sample chamber therefore, is not representative of the fluid thickness in the well.
b) A low cost and reliable device isn't available for retrieving a representative thickness of floating contaminant as well as a representative water sample.
c) Where attempts have been made to provide an adapter to a standard bailer to provide a wider inlet, the attempts have produced devices with inconvenient and expensive add on accessories that can be forgotten or lost and which require the user to know in advance of sampling whether or not the device will be needed., additionally, the add on parts can and do fall off in the well.
d) They fill slower than desired. The small fluid inlet nozzle and its configuration restricts water flow into the sampler such that only a small volume of fluid enters the nozzle relative to the rate of penetration of the sampler through the contaminant and the device fills slower than desired. Frequently, the small diameter, fluid inlet nozzle facilitates the formation of a meniscus across the nozzle that further restricts the flow of water into the sampler.
e) The exteriors are aerodynamically designed having a tapered or dome shaped bottom that is small at the inlet nozzle, becoming larger at the exterior of the sample chamber, as a result, fluids tend to flow preferentially around the outside of the sampler as it is lowered rather than enter the small fluid inlet nozzle. Layers can be missed and sample time is increased.
f) All existing bailers rely on a one way check valve to let fluid in but not back out. Most bailers of the prior art utilize a ball check, valve, others a flapper or pop-it for this valve, which is located at the extreme bottom of the interior of the sampler. All bailers of the prior art have the valves located at the extreme bottom of the sample chamber. Sediments and solids normally present in the water sample settle out of suspension to the lowest point in the sample chamber where they interfere with the workings of the valve. This condition is made worse in bailers where balls serve as valves, by plugging an inlet hole because the ball rests in the small end of a cone shaped holder which funnels and concentrates sediments directly to the area where the ball is expected to produce a seal. The solids and sediments become trapped under and around the ball, propping it away from its mating sealing surface and causing it to leak excessively, resulting in loss of sample and the need for subsequent re-sampling. Further, the excessive leaking causes potentially contaminated fluid to be released into the surrounding environment or splash the user, which may cause harm.
g) Floating contaminants can be lost out the open tops of the bailers if the technician lowers the bailer below the top surface of the water in the well. Bailers of the prior art that utilize a standard check valve at the top of the sample chamber do not address this problem because the valves are in-line and open in the same direction. Fluid flowing in from the bottom can flow right out the top, therefore continued lowering over fills the bailer. Since the device is usually out of sight at some depth, the technician cannot always know when the chamber is full, but not too full.
h) By their nature, valves used to scal the sample chamber of bailers are restrictive to flow. That is, the passageway through which water flows from the well to the sample chamber is smaller than sampler itself, the inlet, and the sample chamber. Those skilled in the art of valves and fluid flow recognize that valves of this type further create physical impediments to water flow. Bailers of the present art are limited in capability because they are constructed with a fixed distance between the fluid inlet and the restrictive valve. The thickness of floating contaminants can vary greatly from well to well. when the contaminant is a thicker layer it will reach the valve restriction before the full thickness is entrapped. The restriction causes the fluid to enter more slowly while the sampler continues descending at the same rate, thereupon pushing aside some of the sample rather than collecting it. Prior art, including add on devices, do not provide a means for the user to make changes in the field to increase the distance between the fluid inlet and the valve restriction to allow a representative thickness of the floating contaminant to enter and be trapped in the sampler prior to its reaching the valve restriction.
It is readily apparent that an improved and multipurpose groundwater sampler is needed to overcome the drawbacks apparent in the prior art and to render more a reliable, convenient, and cost effective method of sampling groundwater and floating liquid thickness. It is, therefore, to the provision of such an improved multipurpose groundwater sampler that the present invention is directed.